Transport signatures of radial Rashba spin-orbit coupling at ferromagnet/superconductor interfaces

Abstract

Spin-orbit coupling (SOC) emerging at the interfaces of superconducting magnetic tunnel junctions is at the heart of multiple unprecedented physical phenomena, covering triplet proximity effects induced by unconventional (spin-flip) Andreev reflections, giant transport magnetoanisotropies, sizable tunneling anomalous Hall effects, and electrically controlled current-reversing 0–π(-like) transitions in Josephson contacts. Recent first-principles calculations proposed that the Rashba spin-orbit fields in twisted graphene/transition-metal dichalcogenide and van der Waals multilayers can—owing to broken mirror symmetries—exhibit an unconventional radial component (with spin parallel to the electron's momentum), which can be quantified by the Rashba angle θR. We theoretically explore the ramifications of radial Rashba SOC at the interfaces of vertical ferromagnet/superconductor tunnel junctions with a focus on the magnetoanisotropies of the tunneling and tunneling-anomalous-Hall-effect conductances. Our results demonstrate that θR can be experimentally extracted from respective magnetization-angle shifts, providing a robust way to probe the radial Rashba SOC induced by twisted multilayers that are placed as tunneling barriers between ferromagnetic and superconducting electrodes.

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